Documenting examples where `utils.clebsch_gordan` is used to perform custom calculations of power spectrum, etc.

[SanggyuChong]

Hello,

I understand a lot of hard work has gone into coding up the CG utils for rascaline. Having this separate util class and functions allows us to do cool stuff like computing the power spectrum of a descriptor that is the difference between two different spherical expansions.

It would be a lot more helpful, in extension to the API, if there are some documentations of simple yet robust examples that explain how the class and its functions can be used.

Can we organize a task force to get this done one afternoon? Happy to be involved myself 👍

[jwa7]

Thanks @SanggyuChong good point - @PicoCentauri and I will be working on the TensorCorrelator calculator next week which will allow you to correlate arbitrary tensors (in the form of TensorMaps). This can be used, for instance, for SOAP-LODE pxV correlations as you say.

It would be great to get a task force together, maybe where we can explain the API and discuss different use cases, then think about how best to write examples and tutorials :)